Trait QRustProxy 

pub trait QRustProxy {
    type ProxyCppType: QCppProxy<ProxyRustType = Self>;
    type AdapterType: DispatchMetaCall + ?Sized;

    // Required methods
    fn new(
        rust_obj: &Rc<RefCell<Self::AdapterType>>,
        metaobject: &'static DynamicMetaObjectData,
        construction: ConstructionMode,
        on_drop: Box<dyn FnOnce() + 'static>,
    ) -> *mut Self;
    fn get_cpp_proxy(&self) -> *const Self::ProxyCppType;
    fn get_cpp_proxy_mut(&self) -> *mut Self::ProxyCppType;
    fn emit_signal(
        &self,
        mut_ref: &mut Self::AdapterType,
        signal_name: &str,
        argv: &[*const u8],
    );
    fn with_rust_ref<R, F: FnOnce(&Self::AdapterType) -> R>(&self, f: F) -> R;
    fn with_rust_ref_mut<R, F: FnOnce(&mut Self::AdapterType) -> R>(
        &self,
        f: F,
    ) -> R;
    fn get_rust_object_rc(&self) -> Option<Rc<RefCell<Self::AdapterType>>>;
}

QRustProxy defines the Rust-side bridge object that binds:

• A Rust object stored in Rc<RefCell<dyn _>>
• A corresponding C++ QObject-based proxy

Implementations of this trait are the concrete glue layer between Rust and Qt, usually using Cxx.

Purpose

A QRustProxy implementation:

• Stores a raw pointer to the C++ proxy (cpp_proxy)
• Stores access to the Rust object through RustObjAccess<dyn _> (rust_obj)
• Coordinates destruction, layout and Qt meta-object information
• Forwards all foreign function calls to the C++ proxy

Typical structure:

pub struct QObjectProxyRust {
    cpp_proxy: *mut QObjectProxyCpp,
    rust_obj: RustObjAccess<dyn QObjectProxyGet>,
    on_drop: fn(rust_obj: *const u8),
}

Where:

• cpp_proxy points to the actual C++ QObject subclass.
• rust_obj wraps access to the users rust object.
• on_drop cleaning up memory.

Lifetime and Ownership

A QRustProxy instance is heap-allocated and owned through a raw pointer, because its lifetime is jointly managed with C++ code and the C++ side requires a stable, non-movable address.

Destruction is always initiated from the C++ side: the paired CppProxy destructor calls GenericRustProxy::drop_self, which converts the raw pointer back to a Box, invokes the stored on_drop callback, and then drops this instance along with its reference to the Rust object.

The reference held to the user’s Rust object is either strong (Rc) or weak (Weak), depending on the ConstructionMode passed to QRustProxy::new:

• Strong / AtAddress - proxy holds a strong Rc; the proxy pair keeps the Rust object alive (QML-created / OwnedByQml path).
• Weak - proxy holds only a Weak reference; the Rust Rc controls the struct’s lifetime (Rust-created / OwnedByRust path).

Associated Types

ProxyCppType

The concrete C++ proxy type. Has to implement QCppProxy.

AdapterType

A wrapper trait for the interface trait that QtBridge users implement. This wrapper is required because not all traits can be used with dyn and are thus incompatible with RustObjAccess (See “object safety” or “dyn compatibility”).

Required Associated Types

type ProxyCppType: QCppProxy<ProxyRustType = Self>

type AdapterType: DispatchMetaCall + ?Sized

Required Methods

fn new( rust_obj: &Rc<RefCell<Self::AdapterType>>, metaobject: &'static DynamicMetaObjectData, construction: ConstructionMode, on_drop: Box<dyn FnOnce() + 'static>, ) -> *mut Self

Creates a new instance of this struct on the heap and returns a raw pointer to it.

Initializes the proxy pair by:

• Creating a RustObjAccess wrapper for rust_obj, holding either a strong or weak reference depending on construction (see ConstructionMode).
• Constructing the paired C++ proxy and binding it to this Rust-side proxy.
• Storing on_drop for invocation when the C++ proxy is eventually destroyed.

fn get_cpp_proxy(&self) -> *const Self::ProxyCppType

fn get_cpp_proxy_mut(&self) -> *mut Self::ProxyCppType

fn emit_signal( &self, mut_ref: &mut Self::AdapterType, signal_name: &str, argv: &[*const u8], )

fn with_rust_ref<R, F: FnOnce(&Self::AdapterType) -> R>(&self, f: F) -> R

fn with_rust_ref_mut<R, F: FnOnce(&mut Self::AdapterType) -> R>( &self, f: F, ) -> R

fn get_rust_object_rc(&self) -> Option<Rc<RefCell<Self::AdapterType>>>

Returns an owned handle to the Rust object behind this proxy, or None if it has already been dropped (the proxy may outlive a weakly-held object). The handle is typed as the adapter trait object; recovering the concrete type requires a checked reinterpret (see QObjectHolder::qobject_to_rc_ref_cell).

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors